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Would any A320 pilot be able to share any tips regarding maintaining a descent rate for final approach of 4°? Of course this is in case of manual flying.

I know we can use a descent rate of speed*5 rule to assume we're on a 3° descent angle, but what if we need to descend 4° or even 5°? Let's assume no wind and 60 tonnes weight of aircraft.

Lastly if we have a strong headwind or tailwind or crosswind, would the calculated rate of descent in ft/ min need to be adjusted?

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    $\begingroup$ It's great to ask questions, but it does scare me a bit that a pilot of a commercial aircraft as complex and large as the A320 may be asking piloting questions of random strangers (with unknown and undocumented qualifications) on the internet. The Airbus A320 is commonly used by commercial airlines to transport passengers, and as a person who sometimes flies commercial, I hope there is training available elsewhere from official sources who are accountable for providing accurate answers. This SE is nice, but there is zero accountability or guarantee of accuracy of any answer here. $\endgroup$ Commented Oct 2, 2023 at 8:58
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    $\begingroup$ @RockPaperLz-MaskitorCasket Pretty sure the OP flying using a desktop simulator and is not a real pilot. So it's perfectly fine to ask such questions here. $\endgroup$
    – Bianfable
    Commented Oct 2, 2023 at 9:05
  • $\begingroup$ @Bianfable Ah, thanks. Just curious, how did you come to that conclusion? BTW, enjoy reading your posts. $\endgroup$ Commented Oct 2, 2023 at 9:18
  • $\begingroup$ @RockPaperLz-MaskitorCasket Based on previous questions and comments, e.g. this comment. $\endgroup$
    – Bianfable
    Commented Oct 2, 2023 at 9:20
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    $\begingroup$ @Bianfable Good memory (or cross-reference)! I've seen so many errors published on the internet (including from "reliable" sources), that it concerned me that pilots may be considering this site as a place to receive part of their training. I enjoy this site, but for pilots of real aircraft, nothing replaces real training by qualified instructors. For those having fun on their home computers, as you imply, errors aren't going to cause any real problems. $\endgroup$ Commented Oct 2, 2023 at 9:30

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You're in luck: the Airbus A320 flight director has a special mode for exactly this: TRK/FPA (track and flight path angle):

A320 FCU
(image source)

  1. When you are on final approach, press the HDG V/S - TRK FPA pushbutton on the FCU. This changes the HDG (heading) selector to TRK (track) and the V/S (vertical speed) selector to FPA (flight path angle). It also changes how the flight director is displayed on the PFD:

    PFD with flight path director

    Flight Path Director (TRK FPA selected on the FCU)

    The display is an alternate way of transmitting flight director commands.

    • The Flight Path Vector (FPV) symbol illustrates the track and flight path angle actually being flown.
    • The Flight Path Director (FPD) symbol shows the pilot how to intercept and fly the vertical and lateral flight path defined by the FMGC. When the pilot superimposes the FPV and FPD symbols, the aicraft is flying the commanded trajectory.

    (Airbus A320 FCOM - Autoflight - Flight Guidance - Flight Director)

  2. Now select the final approach course on the TRK selector on the FCU.

  3. Then select the desired flight path angle (in your case -4.0 for a 4° descent angle) on the FPA selector.

The flight director will now compute how to stay on the track and descent path, taking all head-/tailwind and crosswind components into account. There is no need to manually calculate what vertical speed is required.

You can also engage the autopilot (or keep the autopilot engaged) and it will follow the flight director guidance. If you want to fly manually, just follow the FPD commands on the PFD.

Note that flying in this mode is usually not required for a non-precision approach (except a LOC approach, which should be flown with LOC and FPA modes) because managed modes are recommended when available:

Managed modes are recommended, but selected mode might be useful in case of system or equipment failures.
It is worth recalling that in selected mode, the Flight Path Angle (FPA) easily permits to follow the published descent gradient, but the pilot must still ensure that the vertical trajectory relative to the touchdown point is precisely followed.

Airbus FCU modes for approach

(Airbus - Safely Flying Non-Precision Instrument Approaches)


For an aircraft without FPA mode, you can estimate the required vertical speed based on your ground speed (sketch not to scale):

Speed Sketch

From basic trigonometry, we know that

$$ \tan(\alpha) = \frac{\text{VS}}{\text{GS}} \quad \Leftrightarrow \quad \text{VS} = \tan(\alpha) \text{GS} $$

You probably don't want to use the same units for GS and VS, so with typical units and $\alpha=4^\circ$ we get

$$ \frac{\text{VS}}{\text{ft/min}} = \tan(4^\circ) \frac{\text{kn}}{\text{ft/min}} \frac{\text{GS}}{\text{kn}} \approx 0.070 \times 101 \times \frac{\text{GS}}{\text{kn}} \approx 7.08 \frac{\text{GS}}{\text{kn}} $$

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  • $\begingroup$ That article sounds like a direct response to Air Canada FPAing a plane into a hill. Note the -3.5 degree angle in that approach. $\endgroup$
    – user71659
    Commented Oct 1, 2023 at 20:30
  • $\begingroup$ Thank you for the detailed response. But what if F.P.A and instruments are not available, and you''re only left with your altitude and distance from TDZE? For a 3° descent I know I can use my IAS to determine my rate of descent to maintain a 3° descent but I'd like to know if there's any such thing for a 4° or 5° descent? $\endgroup$
    – R O
    Commented Oct 1, 2023 at 20:53
  • $\begingroup$ @RO If you have that much instrument failure, you have bigger problems! You need ground speed (GS), not IAS to do this calculation. I added a section to the answer to show how to calculate VS based on GS. $\endgroup$
    – Bianfable
    Commented Oct 2, 2023 at 6:28
  • $\begingroup$ Hi there, thanks again. I appreciate all your detailed answers which are perfectly understandable. Just 1 further question please using trigonometry is absolutely great, but any shortcut just like for a 3° descent we take GSx5 to get the rate of descent in ft/min? And to reassure everyone, I'm not a pilot, neither a student for being a pilot, just a MFS2020 startong 1 year ago and enjoying understanding how all this works.thanks again $\endgroup$
    – R O
    Commented Oct 2, 2023 at 11:27
  • $\begingroup$ @RO See the last formula: for 4° you could use GSx7. For 5° just plug in tan(5°) instead and you'll get something like GSx9. $\endgroup$
    – Bianfable
    Commented Oct 2, 2023 at 11:48

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